Structural and electrical characteristics of high-performance stacked YbTi_xO_y/PbZr_0.53Ti_0.47O₃ gate dielectrics for InGaZnO thin-film transistors

In this paper, we developed high-performance InGaZnO thin-film transistors (TFTs) using three stacked TbTi_xO_y, ErTi_xO_y and YbTi_xO_y/PbZr_0.53Ti_0.47O₃ (PZT) gate dielectrics by rf-sputtering method. The structural properties of stacked TbTi_xO_y, ErTi_xO_y and YbTi_xO_y/PZT dielectric films were studied. Atomic force microscopy, X-ray photoelectron spectroscopy and X-ray diffraction were used to investigate the morphological, chemical and structural features, respectively, of these dielectric films. The inspected structural properties were related to the effecting electrical performances. The InGaZnO TFT device fabricating the stacked YbTi_xO_y/PZT dielectric exhibited the best electrical characteristics, such as a small subthreshold swing of 68 mV/decade, a low threshold voltage of 3 mV, a large electron mobility of 24.4 cm²/V-s, and a high I_on/I_off ratio of 5.91 × 10⁹. We attribute this behaviour to the YbTi_xO_y film having a higher κ value as well as a smoother surface.